http://xdebug.org/docs-profiling2.php

xdebug.ini
xdebug.profiler_enable = "1"
xdebug.profiler_aggregate = On
xdebug.profiler_output_dir = "/tmp"
xdebug.profiler_output_name = "crc32"

; xdebug.remote_enable = "1"
; xdebug.remote_handler = "dbgp"
; xdebug.remote_host = "<your_client_box>.example.com"
; xdebug.remote_mode = "req"
; xdebug.allowed_clients = ""